These two comments assert that the VMPSEmin voltage should not be 26 V but instead should be 21.6 V. I dug through the history and this text was added in Nov 2023, via this presentation:
https://www.ieee802.org/3/da/public/1123/clause169_clean.pdf (though there is a presentation there with markups and I don’t recall if this is something we marked up during the meeting
and imported the edited version:
https://www.ieee802.org/3/da/public/1123/clause169_edits.pdf). Regardless of which file was used, Table 169-1 is the same in both locations:
So VMPSEmin has been 26 V from the start. I’m opposed to lowering the minimum voltage because that will then also lower the guaranteed MPSE power. The average power available to an MPD is already low (26 V * 1 A / 16 nodes = 1.625 W), the
change to 21.6 would reduce by about a quarter watt per MPD, or about 17%. I’ve stated many times, the one complaint we will get after publication is “how do I get more power, I need X more watts for my application.” I’m very focused on optimizing power delivered
to prevent a follow-on standard only to raise the power.
I’d expect a presentation justifying 21.6 V and it will take convincing 75% of the TF to make this change. I will not be one of those 75%.
Regards,
Chad Jones
Principal Engineer, Cisco Systems
Executive Secretary, IEEE 802.3 Working Group
Chair, IEEE P802.3da Task Force
Principal, NFPA 70 CMP3
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